A model for low stress cross-diffusional creep and directional coarsening of superalloys

Journal Article · Mon Sep 01 04:00:00 EDT 1997 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(97)00165-6· OSTI ID:540918

Louchet, F ^[1]; Hazotte, A ^[2]

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1. LTPCM/INPG/UJF, St. Martin d`Heres (France)
2. Ecole des Mines, Nancy (France). Lab. de Science et Genie des Materiaux Metalliques

First stages of high temperature creep along <001> in superalloys containing a large volume fraction of the ordered {gamma}{prime} phase are strongly related with directional coarsening (DC), i.e., rafting of {gamma}{prime} precipitates in planes parallel or perpendicular to the stress axis, depending on the signs of lattice misfit and of external loading (tension or compression). The present paper shows that, in the low stresses case, creep cannot directly involve dislocations, and that the major part of the plastic strain during the coarsening process results from a cross diffusion mechanism driven by the gradients of isostatic pressure between phases (Cross-Diffusional Creep). Here, the authors shall consider for the sake of simplicity the case of a superalloy loaded in tension along a <001> direction, with a negative misfit ({delta} = 2({alpha}{sub {gamma}{prime}} {minus} {alpha}{sub {gamma}})/({alpha}{sub {gamma}{prime}} + {alpha}{sub {gamma}}) < 0), which is by far the most frequent situation, and in which the elastic moduli of both phases are comparable.

• OSTI ID: 540918
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 5 Vol. 37; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CREEP
DEFORMATION
DIFFUSION
HEAT RESISTING ALLOYS
MATHEMATICAL MODELS
MICROSTRUCTURE
PRECIPITATION
STRAINS
STRESSES